Partial Compatibility and the Formation of Thickened,Shrink-Resistant Thermoset Moulding Compounds

Abstract

This paper describes a new class of thermosetting polymer blends. The blends are now used commercially in the manufacture of sheet moulding compounds (SMC) where they exhibit important advantages compared with conventional systems. The new compositions comprise a cross-linkable base resin and unsaturated monomer in which the base resin is dissolved and a saturated additive resin which has a crystalline melting temperature T _m below the temperature T _r at which cross-linking occurs. Between T _r and T _m the additive and base resin form a single liquid phase, which on cooling thickens reversibly to a leathery sheet with no bulk phase separation. The paper describes the mechanisms underlying this viscosity switch phenomenon and the partial compatibility criterion used to select the resin-additive combinations which exhibit this behaviour.

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References

[1] Meyer R W 1987 Polyester Molding Compounds and Molding Technology (London: Chapman & Hall)

[2] Selley J E 1989

Unsaturated polyesters

Encyclopedia of Polymer Science and Engineering (New York: Wiley) p 411-411

[3] Bush S F 1985 Utility and complexity in the selection of polymeric materials 2nd Int. Materials Engineering Conf. (London: IMechE) p 229-229

[4] Thompson S J 1983 Thickened moulding compositions GB Patent 2111513 (to Scott-Bader Company Ltd) (20 July)

[5] Osborne T R and Thompson S J 1990 Thickened moulding composites US Patent 4895895 (to Scott-Bader Company Ltd)

[6] Gibson A G and Payne D J 1988

Injection moulding of SMC with physical thickening

Fibre Reinforced Composites Conf. (FRC 88) (London: Plastics and Rubber Institute) p 11.1-11.1

[7] Bush S F , Methven J M and Blackburn D R 1988

Networks as the basis of pre-thickening SMC

Biological and Synthetic Polymer Networks (Amsterdam: Elsevier) p 321-321

[8] Bush S F, Methven J M and Blackburn D R 1989 New polymer compositions International Patent Application WO 89106258 (13 July)

[9] Utracki L A 1989 Polymer Alloys and Blends (New York: Hanser)

10.

[10] Esfandeh M 1994

continuous manufacture of long-fibre reinforced thermoset injection moulding compounds

UMIST Polymer Engineering Report (December)

11.

[11] Blackburn D R 1989 New process for sheet moulding compounds MSc Thesis University of Manchester

12.

[12] Hill T L 1960 Introduction to Statistical Thermodynamics (New York: Addison-Wesley) ch 21

13.

[13] Scatchard G 1931 Chem. Rev. 8 8-8

14.

[14] Hildebrand J H 1936 Solubility (New York: Reinhold)

15.

[15] Tompa H 1952 J. Polym. Sci. 8 51-51

16.

[16] Frith E M and Tuckett R F 1951 Linear Polymers (London: Longmans)

17.

[17] van Krevelen D W 1976 Properties of Polymers 2nd edn (Amsterdam: Elsevier)

18.

[18] Gardon J L 1966

The inuence of polarity on the solubility parameter concept

J. Paint Technol. 38 43-43

19.

[19] Small P A 1953

Some factors affecting the solubility of polymers

J. Appl. Chem. 3 61-61

20.

[20] Union Carbide Corp. 1974 Polyester compositions British Patent 1370138

21.

[21] Williams D R and Dugan J A 1972 Improvements to unsaturated polyester resin compositions British Patent 1279387 (to Koppers Co. Inc.)

22.

[22] Toyo Boseki Kaisha 1976 Unsaturated polyester resin composition British Patent 1445926

23.

[23] Walker A C 1971

Some mechanisms of low profile resin system behavior

29th SPE Antec Mtg (New York: Soc. Plastics Engineers) p 454-454

24.

[24] Williams J J et al 1984

A model for phase separation during a thermoset polymerization

Am. Chem. Soc. Symp. Ser. 208 195-195

25.

[25] Hindersinn R R and Selley J E 1976 Tack-free polymerizable polyester compositions US Patent 3994853 (to Hooker Chemicals & Plastics Co.)

26.

[26] Hansen C M 1967 J. Paint Technol. 39 194-194, 511-511

27.

[27] Brydson J A 1982 Plastics Materials 4th edn (London: Butterworth) p 80-80